The invention relates to an electronic contactor controller for regulating the direct current feed in a circuit with a fluctuating supply voltage, and for a variety of driving coil winding resistances, by means of current switching and having a free-running circuit for holding the contactor during current turn-off phases.
The use of special IC's (integrated circuits) is known for the actuation of electromagnetic actuators employed, for example, as striking magnets in daisy wheel printers, as solenoid, or in magnetic valves. Such a special IC is, for example, the controller module L5832 made by SGS which is described in their "Data Book" published in Jan. 1987. The module permits clocked current regulation of the turn-on current of actuators, with the driver output of the module being employed to actuate the base of a Darlington transistor which serves as the setting device in the current control circuit. The actual value of the turn-on current is detected by a low-ohmic measuring resistor whose measuring input is limited to a voltage signal of 450 mV. At the end of an adjustable turn-on current duration, the module switches the operating current to a holding current which, in contrast to the turn-on current, is not regulated. The turn-on current clock of the module is started only when the operating current has exceeded the predetermined turn-on current value.
U.S. Pat. No. 4,453,194 discloses an integrated bipolar circuit in which a fraction of the total current is branched off for a current measurement and is connected by way of a measuring transistor with a current/voltage converter. The correspondingly generated signal of the current/voltage converter controls the circuit employed to regulate the current. The bipolar technology has the drawback of a limited operating voltage which is not sufficient for orders of magnitude customary in low-voltage networks.